Disclosed herein are phase change inks containing waxes. More specifically, disclosed herein are phase change inks containing paraffin or polymethylene waxes that undergo degradation by biological process during composting to yield carbon dioxide, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and leave substantially no visually distinguishable or toxic residues.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, or the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, or the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Phase change inks frequently contain large amounts of non-compostable waxes, such as high molecular weight polyethylene waxes or the like, with such waxes often being present in phase change inks in amounts of about 50 percent by weight or more.
While known compositions and processes are suitable for their intended purposes, a need remains for improved phase change inks. In addition, a need remains for phase change inks with improved environmental friendliness. Further, a need remains for phase change inks containing an increased percentage of biodegradable and compostable components. Additionally, a need remains for phase change inks that exhibit improved performance in terms of ink rheology, print banding, filtration properties, jetting robustness, and/or thermal stability. There is also a need for phase change inks that can be prepared at reduced costs.